LA-ICP-MS uranium-lead geochronologic data of detrital zircon from a metamorphic rock in the northern Fairbanks mining district, Circle Quadrangle, Alaska, Raw Data File 2025-16, provides uranium-lead (U-Pb) geochronologic single spot zircon data, analyzed using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The detrital zircon (DZ) data come from a metamorphic rock from the Alaska Division of Geological & Geophysical Surveys' (DGGS) geologic mapping project in the northern Fairbanks mining district, covering parts of the Circle A-4, A-5, B-4, and B-5 quadrangles, Alaska. Sample 07JEA354a was collected by the DGGS Mineral Resources Section during a detailed geologic mapping campaign in June 2007. The zircon grain data table contains isotopic and elemental data for each zircon spot analyzed. Both tables have accompanying data dictionaries. These data and report are available from the DGGS website: http://doi.org/10.14509/31685.

This dataset contains U-Pb isotopic data and associated dates for sampled igneous, meta-igneous, and metamorphic rocks of interior and southwestern Alaska. Samples were collected during geologic mapping and mineral deposit research from 2019 to 2023. Mapping and research were funded by the Mineral Resources Program of the U.S. Geological Survey. Mineral separations were conducted at the U.S. Geological Survey mineral separation laboratory in Denver, Colorado and GeoSep Services in Moscow, Idaho. Laser-ablation-inductively-coupled-plasma-mass spectrometry analyses of zircon grains were performed from 2020 through 2024 at the U.S Geological Survey Microbeam Laboratory in Denver, Colorado and at the GeoAnalytical Laboratory, Washington State University, Pullman, Washington by GeoSep Services.

This dataset contains uranium–lead (U-Pb) isotopic data and ages, hafnium (Hf) isotope data, and trace element concentrations of zircon from igneous rocks collected from the Darby Mountains area of the Seward Peninsula, Alaska. The sample suite was collected as part of geological mapping and supporting geochemical and geochronological analysis conducted in 2017. The data tables accompanying this data release report the isotopic composition of U and thorium (Th) measured in each grain, ratios of 207Pb and 206Pb and 235U and 238U, and the age of each grain, plus trace element abundances from the same ablated aliquot, including phosphorus (P), vanadium (V), strontium (Sr), high field strength elements (HFSE), and rare earth elements (REE). Reported Hf (and lutetium, Lu) isotope data includes 176Hf/177Hf, 176Lu/177Hf, and 178Hf/177Hf ratios, calculated epsilon Hf values, and age-corrected isotope ratios and epsilon values.

This data set contains uranium–lead (U-Pb) isotopic data and ages, hafnium (Hf) isotope data, and trace element concentrations of zircon from igneous rocks collected from the Darby Mountains area of the Seward Peninsula, Alaska. The sample suite was collected as part of geological mapping and supporting geochemical and geochronological analysis conducted in 2017. The data tables accompanying this data release report the isotopic composition of U and thorium (Th) measured in each grain, ratios of 207Pb and 206Pb and 235U and 238U, and the age of each grain, plus trace element abundances from the same ablated aliquot, including phosphorus (P), vanadium (V), strontium (Sr), high field strength elements (HFSE), and rare earth elements (REE). Reported Hf (and lutetium, Lu) isotope data includes 176Hf/177Hf, 176Lu/177Hf, and 178Hf/177Hf ratios, calculated epsilon Hf values, and age-corrected isotope ratios and epsilon values.

U-Pb analyses were performed on igneous rocks from the Ray Mountains area of west-central Alaska. These new age analyses will allow us to better evaluate the geochronology of the granitic rocks that are the apparent source of the alluvial REE and tin resources. The plutonic samples have ages ranging from 98.0 +/- 0.9 Ma to 111.6 +/- 1.0 Ma. The sample location coordinates and analytical data tables associated with this report are available in digital format as comma-separated value (CSV) files.

This dataset contains U-Pb isotopic data and associated ages of zircon grains from 27 sedimentary samples and one volcanic ash sample from the Cretaceous Torok and Nanushuk Formations. Seven samples were collected from outcrop and 21 samples were collected from archived core material from oil exploration wells on the North Slope of Arctic Alaska. Zircon grains were analyzed at the University of California, Santa Barbara (UCSB) between 2013 and 2018 using laser-ablation inductively coupled plasma mass spectrometry (LA-ICPMS) techniques. The study was funded by the Energy Resources Program of the U.S. Geological Survey (USGS).

This dataset contains U-Pb isotopic data and associated ages of zircon grains from 27 sedimentary samples and one volcanic ash sample from the Cretaceous Torok and Nanushuk Formations. Seven samples were collected from outcrop and 21 samples were collected from archived core material from oil exploration wells on the North Slope of Arctic Alaska. Zircon grains were analyzed at the University of California, Santa Barbara (UCSB) between 2013 and 2018 using laser-ablation inductively coupled plasma mass spectrometry (LA-ICPMS) techniques. The study was funded by the Energy Resources Program of the U.S. Geological Survey (USGS).

During the 2017 and 2018 field seasons, geologists from the Alaska Division of Geological & Geophysical Surveys (DGGS) conducted geologic mapping and sampling in the Richardson mining district southeast of Fairbanks, including parts of the Big Delta B-4, B-5, B-6, and C-6 quadrangles. The project area has produced approximately 122,000 ounces of gold, mostly from placer mines, and includes the Uncle Sam, Montecristo, Richardson, Tower, and Hilltop lode gold exploration properties. The goal of DGGS's work in this area is to conduct a mineral-resource assessment and to build an improved understanding of the area's geology and controls on gold mineralization to facilitate industry exploration targeting. Uranium-lead (U-Pb) zircon geochronology results presented in this report show that similarly textured quartz-feldspar porphyry intrusions in the project area were generated by both Paleocene (56.8 +/- 0.9 Ma; 18WCW149) and middle Cretaceous (92.0 +/- 0.7 Ma; 18AW002, known as the Democrat Dike) magmatic episodes. The ages of medium-grained plutonic rocks at Birch Lake (92.4 +/- 0.6 Ma; 18ET587) and Gold Run (93.7 +/- 0.7 Ma; 18ET580) lie within error of the age of the hypabyssal Democrat Dike, indicating that the present-day depth of exposure juxtaposes rocks that were buried at widely different crustal depths during the middle Cretaceous. Phaneritic granodiorite near the Democrat prospect yielded a zircon age of 110.7 +/- 1.3 Ma (18RN565), extending the magmatic history of the prospect into the Early Cretaceous. Amphibolite-facies augen orthogneiss yielded a Late Devonian zircon age of 364.5 +/- 6.0 Ma (18ET040), consistent with similar rocks in the Lake George assemblage. Detrital zircons analyzed from siliciclastic schist along the Richardson Highway (18AW021) contain prominent age populations at 1.8 and 2.6 Ga, consistent with a Laurentian cratonic source and consistent with other results from parautochthonous North America. Pelitic schist from the Hilltop prospect (18TJN372) yielded a relatively small number (n=32) of zircon grains that define small age populations between ca. 1.7 and 1.5 Ga. All components of this data release are available on the DGGS website: http://doi.org/10.14509/30555.

This data release includes laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) U-Pb zircon geochronology data to determine the ages of Challis igneous rocks in the Thunder Mountain volcanic field and dikes west of the volcanic field, especially in and near the Stibnite-Yellow Pine mining district, ID. These efforts were made to help understand the stratigraphy and lithologic characteristics of the Challis igneous rocks by determining their absolute ages.